Heredity, Natural Selection, and Evolution

Species and Population

What is a species?

A species can be defined in several ways, and scientists will use different definitions depending on whether they are referring to a fossil (extinct) species or a living (extant) one. For example, an extant species can be defined as all the individuals of all the populations capable of interbreeding. A group of populations that are evolutionarily distinct from all other populations may also be defined as a species, even if they are incapable of inter-breeding due to extinction.